A compact folded-patch UHF RFID tag antenna (30 mm × 30 mm × 3 mm or 0.0912λ × 0.0912λ × 0.009λ) is proposed for metallic surface applications. Two large C-shaped slots, which can be easily tuned by adjusting their lengths, are incorporated into the folded-patch for providing tuning mechanisms that can be employed in the production line for tuning the tag resonant frequency on the fly. The slots are tactfully embedded into the patch structure so that they occupy no footprint. The slots are large enough so that their lengths can be easily adjusted by employing a penknife and some copper tapes. This provides an impromptu tuning mechanism so that the tag resonant frequency can be easily corrected in the production line. With reference to the effective isotropic radiated power of 4 W, the proposed tag antenna can be read from 10 m on metal. The read range is found to be able to go beyond 5.5 m when the tag is placed on a dielectric with permittivity ranging from 1 to 12.
1. UHF RFID Tags, "Smart retail solution,", http://www.thinkgo.co/pinguan-iot-technology-co-ltd-rfid-label-15833051498388722.html.
2. Dobkin, D. M. and S. M. Weigand, "Environmental effects on RFID tag antennas," IEEE MIT-S Int. Microw. Symp. Dig., 135-138, Jun. 2005, doi: 10.1109/MWSYM.2005.1516541. doi:10.1049/el.2013.2671
3. Park, I. Y. and D. Kim, "Artificial magnetic conductor loaded long-range passive RFID tag antenna mountable on metallic objects," Electron. Lett., Vol. 50, No. 5, 335-336, Feb. 2014, doi: 10.1049/el.2013.2671. doi:10.1109/LAWP.2012.2227291
4. Babar, A. A., T. Björninen, V. A. Bhagavati, L. Sydänheimo, P. Kallio, and L. Ukkonen, "Small and flexible metal mountable passive UHF RFID tag on high-dielectric polymer-ceramic composite substrate," IEEE Antennas Wave Propag. Lett., Vol. 11, 1319-1322, 2012, doi: 10.1109/LAWP.2012.2227291. doi:10.1109/TAP.2016.2633903
5. Bong, F. L., E. H. Lim, and F. L. Lo, "Flexible folded-patch antenna with serrated edges for metal-mountable UHF RFID tag," IEEE Trans. Antennas Propag., Vol. 65, No. 2, 873-877, Feb. 2017, doi: 10.1109/TAP.2016.2633903. doi:10.1109/TAP.2018.2821702
6. Ng, W. H., E. H. Lim, F. L. Bong, and B. K. Chung, "Folded dipolar patch antenna with tunable inductive slots and stubs for UHF tag design," IEEE Trans. Antennas Propag., Vol. 66, No. 6, 2799-2806, Jun. 2018, doi: 10.1109/TAP.2018.2821702.
8. Bong, F. L., E. H. Lim, and F. L. Lo, "Compact folded dipole with embedded matching loop for universal tag applications," IEEE Trans. Antennas Propag., Vol. 65, No. 5, 2173-2181, May 2017, doi: 10.1109/TAP.2017.2676776.
9. Monza R6 Tag Chip Datasheet, Rev 3, document IPJ-W1700, Impinj, Inc., Seattle, WA, USA, Dec. 2014. doi:10.1049/el.2012.2813
10. Manzari, S., S. Pettinari, and G. Marrocco, "Miniaturised wearable UHF-RFID tag with tuning capability," Electron. Lett., Vol. 48, No. 21, 1325-1326, Oct. 2012, doi: 10.1049/el.2012.2813.
15. Björninen, T., A. A. Babar, L. Ukkonen, L. Sydanheimo, A. Elsherbeni, and J. Kallioinen, "Compact metal mountable UHF RFID tag on a Barium Titanate based substrate," Progress In Electromagnetics Research C, Vol. 26, 43-57, 2012. doi:10.2528/PIERC15071501
16. Tao, B., H. Sun, and O. M. Ramahi, "RFID tag antenna for metallic or non-metallic surfaces," Progress In Electromagnetics Research C, Vol. 59, 51-57, 2015.
17. Lee, S. R., E. H. Lim, F. L. Bong, and B. K. Chung, "Miniature folded patch with differential coplanar feedline for metal mountable UHF RFID tag," IEEE J. RFID, Vol. 68, No. 1, 152-160, Jan. 2020. doi:10.1109/TAP.2019.2940521
18. Niew, Y. H., K. Y. Lee, E. H., F. L. Bong, and B. K. Chung, "Miniature dipolar patch antenna with nonresonating ring for metal-insensitive UHF RFID tag design," IEEE Trans. Antennas Propag., Vol. 68, No. 3, 2393-2398, Mar. 2020. doi:10.1109/LAWP.2011.2148151
19. Son, H. W. and S. H. Jeong, "Wideband RFID tag antenna for metallic surfaces using proximity-coupled feed," IEEE Antennas Wireless Propag. Lett., Vol. 10, 377-380, 2011. doi:10.1109/LAWP.2013.2281842
20. Zhang, J. and Y. Long, "A miniaturized via-patch loaded dual-layer RFID tag antenna for metallic object applications," IEEE Antennas Wireless Propag. Lett., Vol. 12, 1184-1187, 2013.